Shikaku, Cellblocks & Rectangles: A Puzzle With Many Names

If you have ever solved the daily Cellblocks in The Guardian, drawn boxes in a "Rectangles" puzzle, or played something called "Divide by Box," here is a small revelation: they are all the same puzzle. Its real name is Shikaku, a Japanese logic puzzle, and it has collected more aliases than almost any other puzzle in the genre. That is great news if you love it under one name and want more of it, because once you know what to search for, a whole world of puzzles opens up. This guide untangles the names, explains which is used where, and helps you find the puzzle no matter what it is called. Whatever name brought you here, you can play it now.

One puzzle, many labels

Before the names, the puzzle. Whatever it is called, the game is the same: you divide a grid into rectangles, so that each rectangle contains exactly one number, and that number equals the rectangle's area (how many cells it covers). Every cell ends up inside exactly one rectangle, and the rectangles never overlap. That single elegant idea is the whole game, and every name below points to it. (For the full how-to, our rules page walks through it.)

So why the pile-up of names? Because this puzzle was published and rebranded independently by a Japanese publisher, a British newspaper, and assorted puzzle books, and none of them agreed on a single title.

Shikaku: the original name

Shikaku is the Japanese name and the one used worldwide in puzzle circles. It comes from the phrase 四角に切れ (shikaku ni kire), which means roughly "cut it into squares," a perfect description of what you do. It is the name we use here, and the term you will see most often on dedicated puzzle sites and in the puzzle press. If you want the canonical name, this is it. (You will occasionally see it romanised as "Sikaku," especially in German puzzle archives, but that is the same word.)

Cellblocks: the Guardian name

In the United Kingdom, many people know this puzzle as Cellblocks, the name used by The Guardian newspaper for its syndicated daily version. If you have been doing Cellblocks in the paper and came online looking for more, you may have struggled to find them, because the puzzle is far easier to find under "Shikaku." Now you know: a Cellblocks puzzle is a Shikaku puzzle, with identical rules. Search for "shikaku" and you will never run dry again.

Divide by Box and Rectangles: the descriptive names

The puzzle also travels under a couple of plain-spoken descriptive names:

• Divide by Box is Nikoli's official English name for it (an earlier version was Divide by Squares). It describes the goal literally: divide the grid into boxes. If you met the puzzle in a Nikoli book, this is likely the name you saw.
• Rectangles is the most generic label, used in various puzzle collections. It is accurate but a little ambiguous, since "rectangles" can also mean a geometry exercise, which is why the more distinctive "Shikaku" is the preferred search term.

A few rarer names exist too, such as Number Area, but they are seldom used. Across all of them, the rules never change.

How to recognise it, whatever it's called

Spotting this puzzle in the wild is easy once you know the tell. Look for:

• A grid with numbers scattered in some cells.
• An instruction to divide the grid into rectangles (or boxes), one number per rectangle.
• The rule that each number equals the size of its rectangle.

If a puzzle has those features, it is this one, whether the title says Shikaku, Cellblocks, Rectangles, or Divide by Box. You already know how to play it.

The tangle of names is really a sign of how widely this puzzle has spread, picked up and rebranded by newspapers, publishers and apps around the world because the core idea is so good. Now that you can see through the aliases, there is only one thing left to do: solve one. Play Shikaku now, or learn the rules first.

Frequently asked questions

Is Cellblocks the same as Shikaku?

Yes. Cellblocks is the name The Guardian newspaper uses for Shikaku, the Japanese logic puzzle where you divide a grid into rectangles so each contains one number equal to its area. The rules are identical; only the name differs. If you enjoy the Guardian's daily Cellblocks, searching for "Shikaku" will find you many more.

What does "shikaku" mean?

Shikaku comes from the Japanese phrase 四角に切れ (shikaku ni kire), meaning roughly "cut it into squares." It describes the puzzle's goal of dividing the grid into rectangular pieces. The word "shikaku" itself relates to "square" or "quadrilateral."

What is the "Divide by Box" puzzle?

Divide by Box is Nikoli's official English name for Shikaku (an earlier version was "Divide by Squares"). It is the same puzzle: split the grid into boxes so that each box holds exactly one number, and that number equals the number of cells in the box.

Why does Shikaku have so many names?

The puzzle was published and rebranded independently by different sources. "Shikaku" is the original Japanese name, "Cellblocks" is The Guardian's name, "Divide by Box" is Nikoli's English name, and "Rectangles" is a generic description. They all refer to the same puzzle with the same rules.